Biodiversity restoration of formerly extracted raised bogs: vegetation succession and recovery of other trophic groups

Central European raised bogs are unique and fragile ecosystems inhabited by specialists of higher plants, fungi, and insects. Many of these ecosystems have suffered and are still suffering due to peat harvesting and drainage. The respective specialists, so-called tyrphobionts, and their abundance can serve as good indicators of restoration processes after the disturbance. Various taxonomic groups may differ in the response to the processes. This study shows successional trends in two disturbed raised bogs compared to adjoining undisturbed reference raised bogs. During the growing season of 2019 we compared species richness of successional stages with reference sites for the following five groups of organisms: vascular plants, mosses, fungi, butterflies, and moths. After three decades of spontaneous succession, the species composition did not reach the reference site for any taxonomic group. Instead an alternative, near-natural woodland developed. The different groups of organisms exhibited very similar trends in species richness and participation of tyrphobionts. About half of these specialists occurring at the reference sites were able to colonise the disturbed sites, but mostly in low quantity. Water table and pH appeared significant environmental variables. It seems that habitat limitations play a more important role than dispersal limitations in this restoration process. More successful restoration might be possible by substantially increasing the water table in the disturbed raised bogs.